Funds are requested to permit an upgrade of the capabilities of the Midwest Center for Mass Spectrometry (MCMS) to support collaborative research and service for NIH-supported investigators. One facet of the proposed upgrade is to add an ion trap mass spectrometer to the center to promote collaborative research in gas-phase organometallic chemistry. In addition, the instrument will be used to obtain routine chemical ionization spectra as a service to clients of the facility. The ion trap will replace a nine year old medium performance mass spectrometer (Kratos MS-80), which is of diminished utility because of the reduced need for trace analysis and EI mass spectra. The proposed spectrometer will serve to advance a growing interest in metal ion chemistry. The second goal of the upgrade is to improve the capability for obtaining high resolution EI, CI, FAB, and collisional activation decomposition (CAD) mass spectra with two high performance sector instruments: Kratos MS-50 double focusing and Kratos MS-50 triple analyzer mass spectrometers. Both are equipped with data systems comprised of archaic hardware and software that are not only inadequate but also nearly impossible to maintain. The updated mass spectrometers will be used to support collaborative research aimed at (1) identifying nucleic acid materials that are modified by polycyclic aromatic hydrocarbons and (2) determining structural modifications of peptides. Furthermore, improved service will be offered for local NIH-supported investigators, who need to prove structure of new organometallic compounds, and for at least ten NIH-funded researchers from outside the University of Nebraska. These latter scientists currently submit nearly 40% of the challenging service projects handled at the MCMS.